PHOENIX -- In the chaotic minutes after Wednesday's workplace shooting in Phoenix, one witness chased after the gunman, got his license plate number and got shot at for his trouble.

Oscar Bejar, 20, works in maintenance at the Phoenix office building where the shooting happened. He said he was aware of two men in suits who were speaking with an older gray-haired man near the elevators.

"As soon as the doors close, going up, his finger is already on [button] one shaking," said Bejar. "The doors open on number two and his finger is still there. I popped off."

But the older man, now identified as Arthur Harmon, stayed on, returning to the lobby. That's when Bejar heard several shots fired, looked down from the balcony and saw a man lying on the ground.

"I'm like, 'Oh, that's the older guy with us on the elevator, he's probably going to go help him out," Bejar said. "The guy that was screaming, he walks up to him and shoots him in the head."

As Harmon left out the back, Bejar said he checked that he had his keys and raced out the front and followed Harmon.

"He pulls over, so I pull over 10 cars away from him then he opens his door, I thought he was going to run," Bejar said. "Thirty seconds later he walks out with a rifle pointing at me and that's when I hit reverse on my car and swerved back onto 16th Street, popped a 180 in the middle of the street and just left."

But first Bejar memorized the car's make and model along with its license plate.

"At that time I was scared for my life," Bejar said. "At first I wasn't. I just wanted to see where he was going, you know, so he could get some justice served."

Bejar said he was just thinking of those people he saw shot and their families.

"I couldn't believe it because it was all adrenaline rush, but then thinking about it, he was shooting at me and I could have got hit or something," Bejar said. "But at first I was just doing it for them, just trying to help out."